Launching the latest effort in her Art for Freedom campaign with an event in New York City, the singer delivered a moving rendition of Smith's 1997 lament, "Between the Bars."

In a 2006 interview with Q magazine, Madonna was asked which song of the last 20 years she wished she'd written. Her answer: Elliott Smith's "Between the Bars," an aching ballad the late artist contributed to the Good Will Hunting soundtrack. On Tuesday night at an event in Manhattan launching the short film, secretprojectrevolution, part of her Art for Freedom campaign, Madonna sang the song she wished was hers.

After being dragged on stage by two actors dressed as police officers, one of whom shoved a microphone in her hand, Madonna delivered a delicate and emotional rendering of the beloved song while accompanied only by a piano.

Halfway through the performance, a kneeling Madonna was accompanied by a masked dancer dressed head-to-toe in black who freed one her bound hands. When the song concluded, the dancer took off his balaclava to reveal his identity: none other than Madonna's 13-year-old son, Rocco.

Madonna's performance of "Between the Bars" comes less than a month before the 10th anniversary of Smith's death. The singer, who scored an Oscar nomination for another Good Will Hunting track, "Miss Misery," died Oct. 21, 2003, of stab wounds to his chest

secretprojectrevolution is Madonna's collaboration with director Steven Klein and centers on the artist being thrown in jail for perceived obscenity. It runs 17 minutes and is available for free download via BitTorrent. The film, which was broadcast via guerilla screenings in 12 cities around the world on Monday and Tuesday, is also the launch of Art for Freedom, an online public art project (in partnership with Vice) that encourages artists to submit videos, music, poetry and photographs that express their meaning of freedom.

Before the film screening and performance, Madonna made a speech before the guests explaining the reasons she made the film.

"This film, aside from my children, is to me the most important thing I've ever done," she said. "The idea of being free, and being able to express myself, not only as an artist but as a human being, is extremely important, and I do not take my freedom for granted. And it seems to me, when I travel around the world, that people are either not free and are fighting for it, or are free and taking it for granted. And both of those situations make me extremely agitated."

"God made art," she continued. "God made human beings to create art. We are channeling God when we make art. I do not doubt that for a minute and it's nobody's business to get in the way of that. Amen."